This invention relates to a silicon integrated circuit including a Hall cell followed by an amplifier and a Schmitt trigger circuit and more particularly to a means for adjusting the operate and release points without substantially altering the variation of those points as a function of temperature.
Integrated circuits including Hall elements are well known. In a silicon integrated circuit the Hall element has a low sensitivity, and other portions of the IC usually contain a differential amplifier for amplifying the low value output voltage from the two sensing or output contacts of the Hall element. In the patent to Anselmo and Genesi U.S. Pat. No. 3,816,766 issued June 11, 1974 and assigned to the same assignee as the present invention, there is described an integrated circuit Hall switch including a Hall element, a Hall voltage amplifier and a Schmitt trigger circuit. This patent describes an approach to circuit design for achieving in a Hall switch a smooth coefficient of the switching or operate-point as a function of temperature. However, it is very difficult to manufacture such Hall switches with predictable operate-points.
It is therefore an object of the present invention to provide integrated circuit Hall switches having a predictable operate-point to within a close tolerance.